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Message-ID: <1337335323.573.7.camel@twins>
Subject: Re: [PATCH 1/2] perf: Add persistent event facilities
From: Peter Zijlstra <peterz@infradead.org>
To: Borislav Petkov <bp@amd64.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>, Ingo Molnar <mingo@elte.hu>,
        Steven Rostedt <rostedt@goodmis.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Borislav Petkov <borislav.petkov@amd.com>
Date: Fri, 18 May 2012 12:02:03 +0200
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On Wed, 2012-03-21 at 15:34 +0100, Borislav Petkov wrote:
> From: Borislav Petkov <borislav.petkov@amd.com>
> 
> Add a barebones implementation for registering persistent events with
> perf. For that, we don't destroy the buffers when they're unmapped;
> also, we map them read-only so that multiple agents can access them.

> +static struct perf_event *perf_add_persistent(struct perf_event_attr *attr,
> +					      int cpu, unsigned nr_pages)
> +{
> +	struct ring_buffer *buffer;
> +	struct perf_event *event;
> +
> +	event = perf_event_create_kernel_counter(attr, cpu, NULL, NULL, NULL);
> +	if (IS_ERR(event))
> +		return event;
> +
> +	buffer = rb_alloc(nr_pages, 0, cpu, RING_BUFFER_WRITABLE);

Uh what?